Re: git: ce881170088c - main - atkbd: Disable periodic polling by default.

Warner Losh <imp_at_bsdimp.com> wrote on
Date: Wed, 5 Jan 2022 17:06:35 -0700 :

> On Wed, Jan 5, 2022 at 5:04 PM Gleb Smirnoff <glebius_at_freebsd.org> wrote:
> 
> > On Wed, Jan 05, 2022 at 04:18:25PM -0700, Warner Losh wrote:
> > W> On Wed, Jan 5, 2022, 3:47 PM Gleb Smirnoff <glebius_at_freebsd.org> wrote:
> > W>
> > W> > On Wed, Jan 05, 2022 at 08:13:03PM +0000, Alexander Motin wrote:
> > W> > A> commit ce881170088c4c98c036fe561f8ee8413c2e2585
> > W> > A> Author:     Alexander Motin <mav_at_FreeBSD.org>
> > W> > A> AuthorDate: 2022-01-05 20:00:36 +0000
> > W> > A> Commit:     Alexander Motin <mav_at_FreeBSD.org>
> > W> > A> CommitDate: 2022-01-05 20:12:58 +0000
> > W> > A>
> > W> > A>     atkbd: Disable periodic polling by default.
> > W> > A>
> > W> > A>     It is one of the few remaining Giant-locked callouts.  It
> > would be
> > W> > A>     good to remove it, not mentioning that polling itself is not
> > good.
> > W> > A>
> > W> > A>     If this cause keyboard/mouse freezes on some hardware, please
> > set
> > W> > A>     loader tunable hw.atkbd.hz=1 as workaround and report the
> > issue.
> > W> > A>
> > W> > A>     Submitted by:   imp, jhb
> > W> >
> > W> > Lame question: this is related only to a keyboard plugged into PS/2,
> > isn't
> > W>
> > W> Yes. I think this part of the code is only for "legacy" keyboards. I
> > don't
> > W> think mice are affected, but since both attach to the keyboard
> > controller
> > W> there is a tiny chance mice might be affected in some weird hardware...
> >
> > I'd even say to legacy mainboards. Cause I have PS/2 keybooard plugged into
> > USB port and AFAIU it is not affected by this change in any way.
> >
> 
> correct. Going through USB is unaffected.
> 
> 
> > I think that even if this change creates some regression, we never know
> > that.
> > Nobody would today run so old mainboard as a desktop. Might have it as a
> > headless appliance.
> >
> 
> You'd be surprised what people run today :(.

Hmm. The ThreadRipper 1950X that I have access to has a PS/2 port
and has a PS/2 keyboard plugged into it.

As I remember, this happened because something happened in the past
that lead to things not getting to the point that the USB keyboard
could be used but the PS/2 keyboard still could be used to get past
the issue. (Not that I remember the details any more.) The PS/2
keyboard was left in place in case such a thing ever happens again.

> Doing the graphics stuff has
> shown
> me that. Nobody would build a new one today, but there's lots of systems
> that have
> been around a few years that have keyboards connected via PS/2.

Yep.

> I doubt,
> though,
> any will see a regression because of the extreme age of this workaround.


===
Mark Millard
marklmi at yahoo.com